Expansion joint cover assembly

ABSTRACT

An expansion joint cover assembly for mounting on structural sections disposed in spaced relation to define an elongated joint therebetween includes a rigid bridging member which is generally arch-shaped in cross section and of sufficient width to span the joint to be covered and the bridging member has opposite side edge portions each slidingly engaging an inclined surface of a base wall of a respective one of a pair of base members each secured to a respective structural section and having an end wall extending from the respective base wall thereby defining a cavity to receive joint filler material having opposite side edges each bonded to the end wall of a respective one of the base members and the joint filler material has a center portion thereof supported on the bridging member whereby the bridging member is moved relative to an exposed surface of the joint filler material in response to movement of the structural sections to accommodate flow of said joint filler material.

United States Patent [1 1 Ball er ct al.

[451 Nov. 26, 1974 EXPANSION JOINT COVER ASSEMBLY [75] Inventors: ClaudeP. Balzer; Edward M.

Corman; Almer A. Reiff; Michael 1). Henry, all of Wichita, Kans.

[73] Assignee: Balco, Inc., Wichita, Kans.

[22] Filed: Aug. 15, 1973 [21] Appl. No.: 388,470

[52] US. Cl 52/396, 52/468, 52/471, 52/573 [51] Int. Cl E04b 1/68 [58]Field of Search 52/396, 468, 471, 573; 404/68, 47, 56, 57, 66

[56] References Cited UNITED STATES PATENTS 3,527,009 9/1970 Nyquist52/396 X 3,732,021 5/1973 Rizza et al. 404/57 8/1973 Balzer et a1 52/396X Primary ExaminerErnest R. Purser Assistant Examiner-Carl D. FriedmanAttorney, Agent, or Firm-Fishburn, Gold & Litman 5 7] ABSTRACT Anexpansion joint cover assembly for mounting on structural sectionsdisposed in spaced relation to define an elongated joint therebetweenincludes a rigid bridging member which is generally arch-shaped in crosssection and of sufficient width to span the joint tobe covered and thebridging member has opposite side edge portions each slidingly engagingan inclined surface of a base wall of a respective one of a pair of basemembers each secured to a respective structural section and having anend wall extending from the respective base wall thereby defining acavity to receive joint filler material having opposite side edges eachbonded to the end wall of a respective one of the base members and thejoint filler material has a center portion thereof supported on thebridging member whereby the bridging member is moved relative to anexposed surface of the joint filler material in response to movement ofthe structural sections to accommodate flow of said joint fillermaterial.

11 Claims, 3 Drawing Figures EXPANSION JOINT COVER ASSEMBLY The presentinvention relates to expansion joint cover assemblies for buildings andmore particularly to an expansion joint cover assembly for coveringadjacent portions of spaced structural sections which are prone to varyin position relative to each other.

It is well known that in building sections of monolithic concrete,concrete blocks, bricks, and the like, relatively long walls, floors,and ceilings must have expansion joints to prevent cracks due toexpansion and contraction. Earth movement also necessitates makingportions of such building structures in sections with expension jointstherebetween to accommodate expansion, contraction, and movement, eventhose caused by earthquake tremor.

It has been the practice in the construction field, in constructingbuildings using a plurality of structural sections, to space theindividual sections of the building from each other whereby portions ofthe structural sections confront each other across an intermediate zone.Such an intentional zone or space is commonly known as an expansionjoint and allows relative movement of the structural sections inresponse to temperature changes, earth movement and the like, andthereby prevents stress in the sections with the resulting cracking. Theexpansion joint or space between the sections, if left exposed, isunsightly and prevents a complete closure to the weather, therefore, itis desirable that an expansion joint cover be provided which seals outweather, deleterious material, and accommodates the relative movement ofthe adjacent sections.

The principal objects of the present invention are: to provide anexpansion joint cover assembly for mounting on structural sectionsdisposed in spaced relation to define an elongated joint therebetweenwherein the assembly has a polyurethane elastomer joint filler having acenter portion thereof supported on a bridging member having a raisedcenter portion and opposite side edge portions slidingly supported oninclined surfaces so that relative movement of the structural sectionseffects movement of the center portion of the bridging member relativeto an exposed surface of the joint filler material to accommodate flowthereof; to provide such an expansion joint cover assembly adapted tomaintain substantial surface continuity across the elongated jointbetween adjacent structural sections; to provide such an expansion jointcover assembly adapted to support loads passing across the elongatedjoint; to provide such an expansion joint cover assembly having pointsof weakness adjacent the bond of a center portion of the joint fillermaterial to the enlarged center portion of the bridging member to permitstretching of the tiller material without breaking bond at the sideedges thereof; to provide such an expansion joint cover assembly whereinas the joint contracts the bridging member is moved along the slopes ofthe respective base members to move the center portion of the bridgingmember away from the exposed face of the joint filler material andthereby increasing the space available for the center portion of thejoint filler material to flow; to provide such an expansion joint coverassembly such that when the joint expands the joint filler materialstretches adjacent the center area thereof and the bridging member movesalong the slopes of the base member to move the center portion of thebridging member toward the exposed face of the joint filler material andthereby maintain constant support for the joint filler material; and toprovide such an expansion joint cover assembly which is economical tomanufacture, easily installed, convenient to repair or replace, whichcan be mounted on exterior or interior surfaces, which is decorativewhen installed, which permits multiple, directional relative movement ofthe building sections at the joint therebetween and which isparticularly well adapted for the proposed use.

Other objects and advantages of this invention will become apparent fromthe following description taken into connection with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and include anexemplary embodiment of the present invention and illustrate variousobjects and features of the expansion joint cover assembly.

FIG. l is a partial perspective view of an expansion joint coverassembly embodying features of the present invention and shown in placeof spaced structural sections and in covering relation to an expansionjoint between the spaced structural sections.

FIG. 2 is an exploded perspective view showing the components of theexpansion joint cover assembly.

FIG. 3 is a transverse sectional view taken on line 3-3, FIG. 1.

Referring more in detail to the drawings:

As required, detailed embodiments of the present invention are disclosedherein, however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention which may be embodied in variousforms, therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting but merely as a basis forthe claims and as a repre sentative basis for teaching one skilled inthe art to variously employ the present invention in virtually anyappropriately detailed structure.

In the disclosed embodiment of the present invention, the referencenumeral 1 generally designates an expansion joint cover assembly formounting on structural sections 2 and 3 disposed in spaced relation todefine an elongated joint 4 therebetween. The expansion joint coverassembly 1 includes a bridging member 5 of sufficient strength and widthto span the joint 4 to be covered and the bridging member 5 has oppositeside edge portions 6 and 7 slidingly engaging inclined surfaces 8' and 9of base walls 8 and 9 respectively of a pair of base members 10 and Mrespectively which are secured to the structural sections 2 and 3. Endwalls 12 and 13 extend from and substantially normal to the base walls 8and 9 respectively and cooperate with the bridging member 5 to define areceptacle or cavity 14 adapted to receive joint filler material 15having opposite side edges 16 and 17 bonded to the end walls 12 and 13respectively of the base members 10 and 11. The joint filler material 15has a center portion 18 thereof supported on an enlarged center portionof the bridging member 5 and the bridging member 5 is moved relative toan exposed surface 19 of the joint filler material 15 is response tomovement of the structural sections 2 and 3 to accommodate flow of saidfiller material 15.

Expansion joints in building construction are used primarily to permitexpansion and contraction of the structural sections which result fromchanges in temperature and to accommodate earth movement and the like.Expansion joints are used between sections of floors, between sectionsof walls, between sections of ceilings, between walls and ceilings, andat the intersection of walls and floors. The expansion joint coverassembly of the present invention is capable of being used for all thevarious types of expansion joints. The expansion joint cover assemblymust be capable of expanding and contracting throughout a selecteddesign range.

In the illustrated structure, the end walls 12 and 13 of the basemembers and 11 are substantially perpendicular or normal to exposedsurfaces 20 and 21 of the structural sections 2 and 3 respectively andthe end walls 12 and 13 are substantially parallel with joint faces orsurfaces 22 and 23 of the structural sections 2 and 3 respectively. Arear or hidden face of each of the end walls 12 and 13 is adapted to beanchored to the respective structural section as by a plurality ofspaced projections extending into the respective sections.

The base walls 8 and 9 intersect the joint faces 22 and 23 respectivelyand the base walls 8 and 9 have respective surfaces 8 and 9 whichslidingly support the side edge portions 6 and 7 of the bridging member5 and the illustrated surfaces 8' and 9 are inclined relative to theexposed surfaces 20 and 21 of the structural section 2 and 3respectively. The inclined surfaces 8 and 9 of the base walls 8 and 9may be any desired shape, such as planar, convex, or the like, whichvaries the spacing of the respective surface relative to the exposedsurface 19 of the joint filler material and relative to the exposedsurfaces and 21 of the structural sections 2 and 3 respectively. In theillustrated embodiment, the surfaces are planar and define an acuteangle between same and the respective end walls 12 and 13 whereby acenter portion or the bridging member 5 is moved relative to the exposedsurface 19 of the joint filler material 15 in response to movement ofthe structural sections 2 and 3 to thereby accommodate flow of the jointfiller material 15.

When the exposed surfaces 20 and 21 of the structural sections 2 and 3are to be formed of finishing or surfacing materials 24 and 25respectively, face portions 26 and 27 are formed in the base members 10and 11 respectively and the face portions 26 and 27 extend from the basewalls 8 and 9 and are adapted to be substantially coplanar with thejoint faces 22 and 23 of the structural sections 2 and 3 respectively.The face portions 26 and 27 of the base members 10 and 1 1 aresubstantially parallel with the end walls 12 and 13 whereby the inclinedsurface of the base walls 8 and 9 define an acute angle with the faceportions 26 and 27 respectively, which is equal to the acute anglebetween the base walls 8 and 9 and the end walls 12 and 13 respectively.

The base members 10 and 11 are adapted to be secured to the structuralsections 2 and 3 or to the finishing materials 24 and 25 respectivelyapplied thereto. In the illustrated structure, spaced flanges or ribs 28and 29 extend from the rear or hidden face of the respective base wallsand face portions and cooperate to define an elongated groove in each ofthe base members 10 and 11 which is adapted to receive suitablelongitudinally spaced anchors 30 therein. The anchors 30 are positionedso that they will be covered by the material forming the respectivestructural section or finishing material thereon and, therefore,maintain the respective base member rigidly in place at the edge of theelongated joint 4.

The face portions 26 and 27 have enlarged portions 31 and 32respectively to define extensions of the base walls 8 and 9 into theelongated joint 4.between the structural sections 2 and 3. The enlargedportions 31 and 32 each have surfaces defining elongated grooves 33 and34 respectively therein. The grooves 33 and 34 are positioned in opposedrelation, for a purpose later described.

Flanges 35 and 36 extend from a free end of the face portions 26 and 27respectively and are adapted to engage interfaces 37 and 38 between thestructural section 2 and the finishing material 24 and the structuralsection 3 and the finishing material 25 respectively. The spacingbetween the flanges 35 and 36 and exposed or free edges 39 and 40 of theend walls 12 and 13 respectively corresponds with the thickness of thefinishing materials 24 and 25 on the structural sections 2 and 3.

The bridging member 5 is adapted to support a load applied to the jointfiller material 15, such as a wheel or the like passing over theelongated joint 4. The bridging member 5 is preferably a substantiallyrigid member having sufficient strength and width to span the elongatedjoint 4 throughout a selected design range and has the side edge portion6 and 7 thereof in sliding engagement with the base walls 8 and 9respectively of the base members 10 and 11. The center portion of thebridging member 5 may be any desired shape extending toward the exposedsurface 19 of the joint filler material 15. The illustrated bridgingmember 5 has a generally arch-shaped cross section with the side edgeportion 6 and 7 depending from an arcuate portion which defines thearch-shape. A center portion 41 of the bridging member 5 is centeredbetween the structural section 2 and 3 and is thereby positioned at thecenter of the elongated joint 4. The center portion 41 of the bridgingmember 5 supports the center portion 18 of the joint filler material 15and the center portion 18 is bonded to the center portion 41.

The joint filler material 15 is supported by and positioned inengagement with the bridging member 5 and has the side edges 16 and 17thereof bonded to the end walls 12 and 13 of the base members 10 and 11respectively. The joint filler material 15 has the exposed surface 19thereof substantially coplanar with the exposed surfaces 20 and 21 ofthe structural sections 2 and 3 to thereby provide surface continuityacross the elongated joint 4. The opposite side edge portions of thejoint filler material 15 have a greater thickness than the centerportion 18 of the joint filler material 15. The joint filler material 15is preferably an elastomer or a syn thetic elastomer having goodresistance to abrasion, oil and other chemicals, and having a hightensile strength, such as polyurethane rubber. The joint material alsopreferably has a shore A durometer value in the range of to 70.

It is desirable to prevent bond between the joint filler material 15'and the bridging member 5 except between the center portion 41 of thebridging member 5 and the center portion 18 of the joint filler material15, therefore, suitable means are positioned between adjacent surfacesof the joint filler material 15 and the bridging member 5 to preventbonding therebetween except at the center portions thereof. Paper,plastic thin metal, and like strips have been found to be sufficient toprevent bond between the joint filler material 15 and the bridgingmember 5.

A suitable flexible moisture shield 42 may be included in the assemblyand has side edges 43 and 44 adapted to be received in the grooves 33and 34 respectively of the base members and 11.

The bridging member 5 and the base members 10 and 11 are preferablyformed of metal by extrusion through suitable dies. The anchors 30 arealso preferably metal and may also be formed by extrusion or any othersuitable method. Aluminum has been found to provide sufficient strengthand lightness in weight for the rigid components of the expansion jointassembly Assembly of the expansion joint cover assembly may be in afactory or during construction of a building When the base members 10and 11 are to be installed on a structural section without finishingmaterial thereon, the base members 10 and 11 are suitably positioned informs for the structural sections and suitable anchors 30 arelongitudinally spaced along the grooves defined by the ribs 28 and 29.After the structural sections have cured and the forms have beenremoved, the moisture shield 42, when used, has the edge portions 43 and44 thereof installed in the grooves 33 and 34 in the enlarged portion 31and 32 respectively. The bridging member 5 is then positioned with theedge portions 6 and 7 thereof in engagement with the base walls 8 and 9respectively and the center portion 41 of the bridging member 5 iscentered between the face portions 26 and 27. Suitable bond preventingmaterial 45, such as paper, plastic, thin metal or like strips, ispositioned to cover all of the bridging member 5 except the centerportion 41 thereof. The bond preventing material may also cover exposedsurfaces of the walls 8 and 9. The center portion 41 of the bridgingmember 5 and the end walls 12 and 13 of the base members 10 and 11 arepreferably cleaned and primed with a suitable compound or adhesive. Thejoint filler material 15 is then poured into the cavity 14 defined bythe end walls 12 and 13, exposed portions of the base walls 8 and 9, andthe bridging member 5. When finishing material 24 and 25 is to be placedon the structural sections 2 and 3, the flanges 35 and 36 are positionedin engagement with the interfaces 3'7 and 38 respectively and theanchors are properly positioned in the grooves defined by the ribs orflanges 28 and 29. The base members 10 and 11 are suitably spaced apart,as by blocking or the like, (not shown) and the finishing material isinstalled on the structural sections 2 and 3 respectively. The moistureshield 42, bridging member 5, bond preventing material, and joint fillermaterial 15 are then installed as previously described.

It is to be understood that while I have illustrated and described oneform of my invention, it is not to be limited to the specific form orarrangement of parts herein described and shown.

What we claim and desire to secure by Letters Patent ll. An expansionjoint cover assembly for structural sections disposed in spaced relationand defining an elongated joint therebetween, at least one of saidsections including a horizontal upper surface said assembly comprising:

a. first and second elongated base members each adapted to be secured toa respective one of a first and second spaced structural sections inopposed relation, said base members each having a surface spaced belowsaid upper surface and intersecting a joint face of the respectivestructural section, said base member surface being inclined relative tosaid upper surface;

b. an elongated bridging member for spanning a joint for the lengththereof between the structural sections, said bridging member havingopposite side edge portions each slidingly engaging said surface of arespective one of said base members; and

c. a cured resilient joint filler material positioned for supportingengagement by said bridging member and having opposite side edgesthereof each bonded to a respective one of said base members, said jointfiller material having an exposed surface coplanar with said horizontalupper surface; said inclination of the surfaces of the base members andthe sliding engagement of said side edge portions of bridging membertherewith cooperating in response to movement of the structural membersfor maintaining of the upper surface of the filler materialsubstantially level with said horizontal upper surface of said sections.

2. An expansion joint cover assembly as set forth in claim 1 wherein:

a. said surface of each of said base members is inclined at an acuteangle relative to the exposed surface of the respective structuralsection; and

b. said bridging member has a center portion positioned closer to theupper surface of said joint filler material than said opposite side edgeportions thereof whereby the center portion of said bridging member ismoved relative to the exposed surface of said joint filler material inresponse to relative movement of the structural sections to accommodateflow of said joint filler material and substantially maintain said uppersurface level with said upper surfaces of the sections.

3. An expansion joint cover assembly as set forth in claim 2 wherein:

a. said joint filler material has a center portion thereof bonded to thecenter portion of said bridging member; and

b. means are positioned between adjacent surfaces of said joint fillermaterial and said bridging member to prevent bonding of said jointfiller material to said bridging member except at the respective centerportions thereof.

4. An expansion joint cover assembly for structural sections disposed inspaced relation and defining an elongated joint therebetween saidsections including a horizontal upper surface, said assembly comprising:

a. a pair of elongated base members each adapted to be secured to arespective one of a pair of spaced structural sections in opposedrelation, said base members each having an end wall extendingsubstantially parallel with a joint face of the respective structuralsection and a base wall intersecting the joint face of the respectivestructural section, said base walls having upper surfaces inclined at anacute angle to said upper surface of the sections;

b. an elongated bridging member for spanning a joint between thestructural sections, said bridging member having opposite side edgeportions each slidingly engaging said upper surfaces of the base wall ofa respective one of said base members; and

c. a cured resilient joint filler material positioned in engagement withsaid bridging member and having opposite side edges thereof each bondedto said end wall of a respective one of said base members, said jointfiller material substantially filling the cavity between said end wallsand the bridging member and said upper surfaces of the sections andhaving an exposed surface substantially coplanar with respective uppersurfaces of the structural sections.

5. An expansion joint cover assembly as set forth in claim 4 wherein:

a, said bridging member has a center portion positioned closer to theexposed surface of said joint filler, material than said opposite sideedge portions thereof; and

b. said base wall of each of said base members is angularly inclined todefine an acute angle with said end wall of said respective base memberwhereby the center portion of said bridging member is moved relative tothe exposed surface of said joint filler material in response torelative movement of the structural sections to accommodate flow of saidjoint filler material.

6. An expansion joint cover assembly as set forth in claim 4 wherein:

a. said joint filler material has a center portion thereof bonded to acenter portion of said bridging member; and

means are positioned between adjacent surfaces of said joint fillermaterial and said bridging member to prevent bonding of said jointfiller material to said bridging member except at the respective centerportions thereof.

7. An expansion joint cover assembly as set forth in claim 6 wherein:

a. each of said base members has a face portion extending from said basewall thereof and adapted to be substantially coplanar with the jointface of the respective structural section;

b. said base wall of each of said base members is angularly inclined todefine an acute angle with said respective face portion; and

c. said bridging member has a generally arch-shaped cross sectionwhereby the center portion of said bridging member is moved relative tothe exposed surface of said joint filler material in response torelative, movement of the structural sections to accommodate flow ofsaid joint filler material.

8. An expansion joint cover assembly for structural sections disposed inspaced relation and defining an elongated joint therebetween, saidsections including a horizontal upper surface, said assembly comprising:

a. a pair of elongated base members each having an end wall extendingsubstantially parallel with a joint face of a respective one of a pairof spaced structural sections in opposed relation and a base wall havingan upper surface intersecting the joint face of the respectivestructural section, said upper surface of the base wall being spacedbelow said upper surface of the structural section and inclined relativethereto;

b. means for securing each of said base members to a respective one ofthe structural sections;

c. an elongated bridging member for spanning a joint between thestructural sections, said bridging member having opposite side edgeportions and each slidingly engaging the upper surface of the base wallof a respective one of said base members, said bridging member having agenerally arch-shaped cross section; and

d. a cured resilient joint filler material positioned in engagement withsaid bridging member and having opposite side edges thereof each bondedto said end wall of a respective one of said base members, said jointfiller material substantially filling the space between said end walls,bridging member and upper surfaces and having an exposed surfacesubstantially coplanar with respective exposed surfaces of thestructural sections, the opposite side edges of said joint fillermaterial, said inclination of said upper surfaces of the base wall andsliding engagement of side edge portions of the bridging membertherewith cooperating to substantially maintain the coplanarrelationship of the exposed surface of the filler material and uppersurfaces of the sections through expansion and contraction of the joint.

9. An expansion joint cover assembly as set forth in claim 8 wherein:

a. said joint filler material is a polyurethane elastomer;

b. the center portion of said joint filler material is bonded to thecenter portion of said bridging member; and

0. means are positioned between adjacent surfaces of said joint fillermaterial and said bridging member to prevent bonding of said jointfiller material to said bridging member except at the respective centerportions thereof.

10. An expansion joint cover assembly as set forth in claim 9 wherein:

a. each of said base members has a face portion extending from said basewall thereof and adapted to be substantially coplanar with the jointface of the respective structural section;

b. said face portions each are adapted to be secured to the respectivestructural section; and

c. said base wall of each of said base members is angularly inclined todefine an acute angle with said respective face portion whereby thecenter portion of said bridging member is moved relative to the exposedsurface of said joint filler material in response to relative movementof the structural sections to accommodate flow of said joint fillermaterial.

]. 1. An expansion joint cover assembly as set forth in claim 8including:

a; a face portion for each of said base members and extending from saidbase wall thereof, said face portions each being adapted to besubstantially coplanar with the joint face of the respective structuralsection; and

b. a flange extending from a free end of each of said face portions andadapted to engage an interface between the respective structural sectionand finishing material thereon.

1. An expansion joint cover assembly for structural sections disposed inspaced relation and defining an elongated joint therebetween, at leastone of said sections including a horizontal upper surface said assemblycomprising: a. first and second elongated base members each adapted tobe secured to a respective one of a first and second spaced structuralsections in opposed relation, said base members each having a surfacespaced below said upper surface and intersecting a joint face of therespective structural section, said base member surface being inclinedrelative to said upper surface; b. an elongated bridging member forspanning a joint for the length thereof between the structural sections,said bridging member having opposite side edge portions each slidinglyengaging said surface of a respective one of said base members; and c. acured resilient joint filler material positioned for supportingengagement by said bridging member and having opposite side edgesthereof each bonded to a respective one of said base members, said jointfiller material having an exposed surface coplanar with said horizontalupper surface; said inclination of the surfaces of the base members andthe sliding engagement of said side edge portions of bridging membertherewith cooperating in response to movement of the structural membersfor maintaining of the upper surface of the filler materialsubstantially level with said horizontal upper surface of said sections.2. An expansion joint cover assembly as set forth in claim 1 wherein: a.said surFace of each of said base members is inclined at an acute anglerelative to the exposed surface of the respective structural section;and b. said bridging member has a center portion positioned closer tothe upper surface of said joint filler material than said opposite sideedge portions thereof whereby the center portion of said bridging memberis moved relative to the exposed surface of said joint filler materialin response to relative movement of the structural sections toaccommodate flow of said joint filler material and substantiallymaintain said upper surface level with said upper surfaces of thesections.
 3. An expansion joint cover assembly as set forth in claim 2wherein: a. said joint filler material has a center portion thereofbonded to the center portion of said bridging member; and b. means arepositioned between adjacent surfaces of said joint filler material andsaid bridging member to prevent bonding of said joint filler material tosaid bridging member except at the respective center portions thereof.4. An expansion joint cover assembly for structural sections disposed inspaced relation and defining an elongated joint therebetween saidsections including a horizontal upper surface, said assembly comprising:a. a pair of elongated base members each adapted to be secured to arespective one of a pair of spaced structural sections in opposedrelation, said base members each having an end wall extendingsubstantially parallel with a joint face of the respective structuralsection and a base wall intersecting the joint face of the respectivestructural section, said base walls having upper surfaces inclined at anacute angle to said upper surface of the sections; b. an elongatedbridging member for spanning a joint between the structural sections,said bridging member having opposite side edge portions each slidinglyengaging said upper surfaces of the base wall of a respective one ofsaid base members; and c. a cured resilient joint filler materialpositioned in engagement with said bridging member and having oppositeside edges thereof each bonded to said end wall of a respective one ofsaid base members, said joint filler material substantially filling thecavity between said end walls and the bridging member and said uppersurfaces of the sections and having an exposed surface substantiallycoplanar with respective upper surfaces of the structural sections. 5.An expansion joint cover assembly as set forth in claim 4 wherein: a.said bridging member has a center portion positioned closer to theexposed surface of said joint filler, material than said opposite sideedge portions thereof; and b. said base wall of each of said basemembers is angularly inclined to define an acute angle with said endwall of said respective base member whereby the center portion of saidbridging member is moved relative to the exposed surface of said jointfiller material in response to relative movement of the structuralsections to accommodate flow of said joint filler material.
 6. Anexpansion joint cover assembly as set forth in claim 4 wherein: a. saidjoint filler material has a center portion thereof bonded to a centerportion of said bridging member; and b. means are positioned betweenadjacent surfaces of said joint filler material and said bridging memberto prevent bonding of said joint filler material to said bridging memberexcept at the respective center portions thereof.
 7. An expansion jointcover assembly as set forth in claim 6 wherein: a. each of said basemembers has a face portion extending from said base wall thereof andadapted to be substantially coplanar with the joint face of therespective structural section; b. said base wall of each of said basemembers is angularly inclined to define an acute angle with saidrespective face portion; and c. said bridging member has a generallyarch-shaped cross section whereby the center portion of said bridgingmember is moved relative to the exposed surface of said joint fillermaterial in response to relative movement of the structural sections toaccommodate flow of said joint filler material.
 8. An expansion jointcover assembly for structural sections disposed in spaced relation anddefining an elongated joint therebetween, said sections including ahorizontal upper surface, said assembly comprising: a. a pair ofelongated base members each having an end wall extending substantiallyparallel with a joint face of a respective one of a pair of spacedstructural sections in opposed relation and a base wall having an uppersurface intersecting the joint face of the respective structuralsection, said upper surface of the base wall being spaced below saidupper surface of the structural section and inclined relative thereto;b. means for securing each of said base members to a respective one ofthe structural sections; c. an elongated bridging member for spanning ajoint between the structural sections, said bridging member havingopposite side edge portions and each slidingly engaging the uppersurface of the base wall of a respective one of said base members, saidbridging member having a generally arch-shaped cross section; and d. acured resilient joint filler material positioned in engagement with saidbridging member and having opposite side edges thereof each bonded tosaid end wall of a respective one of said base members, said jointfiller material substantially filling the space between said end walls,bridging member and upper surfaces and having an exposed surfacesubstantially coplanar with respective exposed surfaces of thestructural sections, the opposite side edges of said joint fillermaterial, said inclination of said upper surfaces of the base wall andsliding engagement of side edge portions of the bridging membertherewith cooperating to substantially maintain the coplanarrelationship of the exposed surface of the filler material and uppersurfaces of the sections through expansion and contraction of the joint.9. An expansion joint cover assembly as set forth in claim 8 wherein: a.said joint filler material is a polyurethane elastomer; b. the centerportion of said joint filler material is bonded to the center portion ofsaid bridging member; and c. means are positioned between adjacentsurfaces of said joint filler material and said bridging member toprevent bonding of said joint filler material to said bridging memberexcept at the respective center portions thereof.
 10. An expansion jointcover assembly as set forth in claim 9 wherein: a. each of said basemembers has a face portion extending from said base wall thereof andadapted to be substantially coplanar with the joint face of therespective structural section; b. said face portions each are adapted tobe secured to the respective structural section; and c. said base wallof each of said base members is angularly inclined to define an acuteangle with said respective face portion whereby the center portion ofsaid bridging member is moved relative to the exposed surface of saidjoint filler material in response to relative movement of the structuralsections to accommodate flow of said joint filler material.
 11. Anexpansion joint cover assembly as set forth in claim 8 including: a. aface portion for each of said base members and extending from said basewall thereof, said face portions each being adapted to be substantiallycoplanar with the joint face of the respective structural section; andb. a flange extending from a free end of each of said face portions andadapted to engage an interface between the respective structural sectionand finishing material thereon.